1. Field of the Invention
The present invention relates to a fluid-pressure boosting cylinder apparatus that is compact, provides a high thrust, and is designed to output the total force of a fluid pressure acting on multiple pressurized surfaces, and in particular, to a fluid-pressure boosting cylinder apparatus having a rotation-preventing mechanism for regulating the free rotation of a piston.
2. Description of the Prior Art
FIG. 7 shows an example of a fluid-pressure boosting cylinder apparatus of this kind. A fluid pressure cylinder body 1 in this cylinder apparatus comprises a cylinder tube 2; and a head cover 3 and a rod cover 4 are screwed into the respective axial ends of the cylinder tube 2 in an air-tight manner.
An outer piston 5 that slides through the cylinder tube 2 in an air-tight manner consists of an outer rod 6 that penetrates the rod cover 4 in an air-tight manner, and A tube head 7 is screwed into the tip of the outer rod 6. An inner rod 9, one end of which is fixed to the head cover 3, penetrates the center of the outer piston 5 in an air-tight manner and has an inner piston 10 attached to its tip. The outer piston 5 and the outer rod 6 can slide freely relative to the inner piston 10 and inner rod 9 fixed to the fluid pressure cylinder body 1.
In addition, an inner tube 9a is provided in the inner rod 9, and the inner rod 9 and the inner tube 9a constitute a double pipe.
In this cylinder apparatus, when compressed air is supplied from a supply and ejection port 12a provided in the head cover 3 to a pressure chamber 14 between the head cover 3 and the outer piston 5 and supplied to a pressure chamber 15 between the inner piston 10 and the tube head 7 through a channel 13a in the inner tube 9a, the outer piston 5, outer rod 6, and tube head 7 integrally move leftward in FIG. 7. In this case, because the thrust of the cylinder apparatus is equal to the total force of fluid pressure supplied to the pressure chambers 14 and 15, this cylinder apparatus provides a larger thrust than a conventional cylinder apparatus having only one piston.
In addition, when compressed air is supplied to a pressure chamber 16 between the outer piston 5 and the inner piston 10 through a channel 13b between the inner rod 9 and the inner tube 9a, the outer piston 5 returns to the illustrated state.
A boosting cylinder apparatus with such a configuration has the advantage of providing high power despite its small size, but is disadvantageous in that a rotation-preventing mechanism for regulating the free rotation of the piston can not be provided easily due to the structure of the apparatus. More specifically, a conventional cylinder apparatus having only one piston allows a rotation-prevention mechanism to be simply provided by using a square shaft and a square hole as the rod and its sliding hole, but in a boosting cylinder apparatus, because the inner piston is slidably accommodated inside the rod, a square shaft cannot easily be used as the rod. In addition, since the high power obtained results in a large torque acting on the rod, a rotation preventing mechanism consisting of such a square shaft and a square hole cannot provide sufficient strength easily.
In addition, a shaft capable of guiding the operation of the piston toward the exterior of the cylinder tube 2 may be provided parallel with the cylinder tube 2 and designed to have a rotation-preventing function. Since the mounting of this shaft, however, may increase the size of the cylinder apparatus or complicate its structure, such a shaft is not desirable.